The present invention relates to a polyurethane elastomer and to a hypoallergenic polyurethane glove for use by surgeons and others which is easily donned, is comfortable on the hand and has good tear resistance prepared therefrom.
Usually, gloves of a flexible nature which fit the hand with a skin-tight fit (so called surgical gloves) are made from rubber compositions such as rubber cements and latexes. These compositions are hyperallergenic and 5% of those who regularly wear these gloves suffer from a type of dermatitis. The cause of the dermatitis is believed to be natural impurities which occur in the rubber latex or additives such as the curing agent, antioxidant, or the like. Attempts to remove these additives and impurities or to reduce them to nonallergenic levels have not been totally successful or economically attractive.
One approach to overcome the allergenicity problem has been to manufacture the glove of a non-allergenic or hypoallergenic biocompatable material. In this regard, Miner et al, U.S. Pat. No. 3,872,515 discloses a flexible glove made using silastic rubber.
Polyurethanes have also been used for this purpose and are very advantageous because they are biocompatible, they can be formed into films with high water vapor transmission, they are cooler to wear, and they are oil resistant and do not swell and bag on the hand in the presence of body oils. They also provide good tactility. However, it is difficult to obtain a polyurethane having good film forming properties that provides a glove that is easily donned and does not constrict the hand.
A number of drawbacks occur when polyurethanes are used in the manufacture of surgical gloves. In particular, due to the higher modulus of many polyurethanes they do not provide a glove that can be easily donned and which is comfortable on the hand. At the same time, it is difficult to modify conventional polymers to increase their softness and reduce modulus. Increasing the amount of soft segment to lower the modulus dilutes the hard segment and gives the polymers high set and creep. On the other hand, where the molecular weight of the soft segment is increased to improve softness, the soft segment often crystallizes and a drastic increase in modulus, directly contra the desired result, occurs. Likewise, where the amount of hard segment is reduced, there is less physical cross-linking and higher set.
The polyurethanes that have been used to fabricate surgical gloves have a much higher modulus than rubber and it has been necessary to use them as relatively thin films typically ranging from about 3.5 to 4.5 mils in thickness. If previous polyurethane films were used in the same thickness as the rubber films used in conventional gloves, the polyurethane gloves would be impossible to don and very uncomfortable to wear. At the same time from a manufacturing standpoint the thin films that have been used have not been completely satisfactory; film quality is not high and there is a high rate of rejection for film leaks.
Thus, there is a need for a non-allergenic polyurethane glove which is easily donned, comfortable and made from a comparatively low modulus polyurethane and, thus, there is a need for a very soft, low modulus polyurethane which has physical properties similar to those of rubber.